[Expansion behavior of intravitreous sulfur hexafluoride in exposure to nitrous oxide]

In experiments with 19 rabbits the changes in volume and concentration of intravitreously instilled sulfur hexafluoride were investigated under normal air conditions (10 rabbits in group A) and with application of laughing, gas to the inspiration system for 3 hours (9 rabbits in group B). Under normal air conditions the SF6 gas bubble attained its greatest volume after 24 hours (twice its initial volume). With the addition of 67% laughing gas to the inspiration system the largest expansion in volume (260%) was found after 3 hours, i.e., at the end of application of laughing gas, and was followed by another peak after 24 hours. With regard to the sulfur hexafluoride concentration in the gas bubble, the results in the two groups were similar. The authors conclude that in retinal surgery with application of sulfur hexafluoride general anesthesia should not include laughing gas.